1. Field of the Invention
The present invention relates to an internal combustion engine control unit for a jet propulsion type watercraft that is powered by a jet propulsion force, and more particularly to a personal watercraft (PWC) which is a jet propulsion type watercraft.
2. Description of the Background Art
FIG. 4 is a perspective view showing the general construction of a PWC which is a jet propulsion type watercraft as disclosed in, for example, U.S. Pat. No. 6,159,059. In the figure, reference number 1 denotes a hull of a PWC; 2 an internal combustion engine which is controlled by an internal combustion engine control unit (ECU, not shown) and that generates a jet propulsion force optimum for driving the PWC, thereby allowing the hull 1 to run. Reference number 3 denotes a throttle valve which adjusts a throttle of the engine 2; 4 an impeller which is directly connected to the engine 2 and makes water drawn from the front of the hull 1 function as a jet propulsion force; 5 a spouting nozzle which spouts jet water generated by the impeller 4; and 6 a steering nozzle which changes the direction of jet water spouted from the spouting nozzle 5.
Reference number 7 denotes a steering handle which steers the direction of the hull 1 and that is coupled with the steering nozzle 6 through a steering cable 9, and it is possible to stir the hull 1 by changing the spouting direction of jet water. Reference number 8 denotes a throttle lever which is coupled with the throttle valve 3 through a throttle cable 10 and can adjust the throttle. The steering handle 7 and the steering nozzle 6 can be coupled not only in the above-mentioned mechanical manner but also in an electric manner such that, for example, a turning angle position of the steering handle 7 is detected, and the steering nozzle 6 is moved by a motor based on the detected signal.
Next, the movement for changing the traveling direction of the hull 1 by a rider who operates the steering handle 7 will be explained with reference to FIG. 5. As shown in FIG. 5A, when the traveling direction of PWC is straight, the rider keeps the steering handle 7 vertically with respect to the traveling direction of PWC. Here, the steering nozzle 6 coupled with the steering handle 7 through the steering cable 9 is set exactly backward, and jet water is spouted backward to generate a jet propulsion force, thereby moving the PWC to move straight ahead.
On the other hand, as shown in FIG. 5B, in the case where it is intended to change the traveling direction of PWC to the left, when the rider turns the steering handle 7 to the left, the steering nozzle 6 moves to the right, and the spouting direction of jet water changes to the right, whereby the traveling direction of PWC can be changed to the left. Also, as shown in FIG. 5C, in the case where it is intended to change the traveling direction of PWC to the right, when the rider turns the steering handle 7 to the right, the steering nozzle 6 moves to the left, and the spouting direction of jet water changes to the left, whereby the traveling direction of PWC can be changed to the right.
In general, it is arranged that the engine rotation speed is defined by a throttle operation performed by the rider. When the rider operates the throttle to open, the engine rotation speed is increased. Thus, the jet propulsion force of PWC is increased, whereby the jet propulsion force is enhanced to allow the PWC to run faster. On the other hand, when the rider operates the throttle to close, the engine rotation speed is in the idle state where it is low. Thus, the jet propulsion force of PWC is reduced, and the running speed is therefore decreased gradually to the state that the PWC stops.
The internal combustion engine control unit (ECU) controls ignition timing, an amount of fuel supply (an amount of fuel spouting and jetting timing), and an amount of auxiliary intake air for the optimum engine performance and characteristics with respect to the degree of opening the throttle, such that the rider can operate and drive the PWC easily.
In the conventional PWC, as the operation inherent to PWC, in order to change the traveling direction of the hull 1, it is necessary to change the spouting direction of jet water. Such can be achieved by operating the steering handle 7. However, when the jet water does not have a propulsion force reaching a predetermined value, the traveling direction of PWC cannot be changed. In other words, it is necessary to operate the steering handle 7 under the condition where the throttle is opened and the engine rotates at a predetermined rotation speed or higher (the state that a jet propulsion force exists). However, even when the steering handle 7 is operated in the state that no jet propulsion force exists, there is an operational performance that it is impossible to change the traveling direction of the hull 1.
When some risk is realized ahead in running, the steering handle 7 is generally turned to the right or to the left so as to change the traveling direction of PWC to avoid the risk. Here, when the engine rotation speed reaches a predetermined value, there is a jet propulsion force enough to change the traveling direction of PWC by the steering handle 7, whereby the risk can be avoided. However, in the case where the risk is recognized when the throttle is nearly closed in the idle state, there was a problem that the risk cannot be avoided because, nevertheless the hull 1 runs at a certain speed by a remaining power depending on the engine rotation speed, a jet propulsion force enough to change the traveling direction of PWC by the steering handle 7 is not obtained.
In this case, it is necessary to open the throttle in addition to the steering handle operation. However, when a rider, especially a beginner, encounters a risk suddenly, he/she operates only the steering handle 7 in a fluster and forgets to open the throttle to generate the jet propulsion force, so that the risk cannot be avoided and a collision, for example, may occur. The PWC becomes popular because of the easier operation and the comfort, and the number of beginners increases, which also increases the number of this kind of accidents.
Further, when a watercraft gets to the shore, it is necessary to adjust the watercraft speed by performing a subtle throttle opening operation. However, it is difficult for a beginner to get to the shore slowly in a stable manner, and the watercraft may bump against the quay, whereby an impact is likely given.
The present invention has been made to overcome the above-described problems. An object of the present invention is to provide an internal combustion engine control unit for a jet propulsion type watercraft which can control an internal combustion engine so that a rider can avoid risks safely.
The internal combustion engine control unit for a jet propulsion type watercraft in accordance with the present invention, includes a throttle operation state detector which detects a state of the throttle operated by a rider, and a controller which, when the throttle open degree detected by the throttle operation state detector is a predetermined value or lower, keeps the rotation speed of the internal combustion engine at a predetermined value for a predetermined period of time after the throttle open degree has reached the predetermined value or lower. Thus, even when the watercraft is running in a state that a jet propulsion force enough to change the traveling direction by a steering handle is not obtained, the extra jet propulsion force which can change the traveling direction can be added quickly, so that the rider can perform the risk avoidance safely.
The internal combustion engine control unit of the present invention may further include an ignition timing controller which controls ignition timing for the internal combustion engine and a fuel supplying amount controller which controls a fuel supplying amount supplied to the internal combustion engine, whereby the rotation speed of the internal combustion engine is increased by using at least one of the ignition timing controller and the fuel supplying amount controller. Thus, even when the watercraft is running without a jet propulsion force enough to change the traveling direction of the watercraft by using a steering handle, the extra jet propulsion force which can change the traveling direction of the watercraft can be added quickly so that the rider can perform the risk avoidance safely.
In addition, the ignition timing is controlled to be earlier than usual. Thus, even when the watercraft is running without a jet propulsion force enough to change the traveling direction of the watercraft by using a steering handle, the extra jet propulsion force which can change the traveling direction of the watercraft can be added quickly so that the rider can perform the risk avoidance safely.
The fuel supplying amount may be controlled to be larger than usual. Thus, even when the watercraft is running without a jet propulsion force enough to change the traveling direction of the watercraft by using a steering handle, the extra jet propulsion force which can change the traveling direction of the watercraft can be added quickly so that the rider can perform the risk avoidance safely.
In the present invention, the fuel supplying amount is controlled by making the fuel supplying timing earlier than usual. Thus, even when the watercraft is running without a jet propulsion force enough to change the traveling direction of the watercraft by using a steering handle, the extra jet propulsion force which can change the traveling direction of the watercraft can be added quickly so that the rider can perform the risk avoidance safely.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.